Abstract
Plants synthesize a variety of metabolites in response to biotic elicitors. To comprehend how the digested cell wall of Piriformospora indica affects the response of ROS burst, antioxidant enzymes, amino acids profiling, and phenylpropanoid compounds such as lignans, phenolic acids, and flavonoids in Linum album hairy roots; we accomplished a time-course analysis of metabolite production and enzyme activities in response to CDCW and evaluated the metabolic profiles. The results confirms that CDCW accelerates the H2O2 burst and increases SOD and GPX activity in hairy roots. The HPLC analysis of metabolic profiles shows that the H2O2 burst shifts the amino acids, especially Phe and Tyr, fluxes toward a pool of lignans, phenolic acids, and flavonoids through alterations in the behavior of the necessary enzymes of the phenylpropanoid pathway. CDCW changes PAL, CCR, CAD, and PLR gene expression and transiently induces PTOX and 6MPROX as the main-specific products of PAL and PLR genes expression. The production of phenolic acids (e.g., cinnamic, coumaric, caffeic, and salicylic acid) and flavonoids (e.g., catechin, diosmin, kaempferol, luteolin, naringenin, daidzein, and myricetin) show different behaviors in response to CDCW. In conclusion, our observations show that CDCW elicitation can generate H2O2 molecules in L. album hairy roots and consequently changes physiological, biochemical, and molecular responses such as antioxidant system and the specific active compounds such as lignans. Quantification of metabolic contents in response to CDCW suggests enzyme and non-enzyme defense mechanisms play a crucial role in L. album hairy root adaptation to CDCW. A summary revealed that the correlation between H2O2 generation and L. album hairy root defense system under CDCW. Increase of H2O2 generation led plant to response against oxidative conditions. SOD, and GPX modulated H2O2 content, Phe, and Tyr shifted to the phenylpropanoid compounds as a precursor of PAL and TAL enzyme, the predominant phenylpropanoid compounds controlled oxidative conditions, and the other amino acids responsible for amino acid synthesis and development stages.